This invention relates to shock absorbers and bushings for the shock absorbers. The shock absorbers are for hitches for trailers on pickup trucks, tractor units and the like for towing larger trailers. In particular the invention relates to shock absorbers for fifth wheel hitches.
Fifth wheel trailer hitches are generally used to tow larger trailers (semi-trailers), where it is desired to locate the center of gravity of the trailer in a more forward position relative to the towing vehicle to improve weight distribution, stability and maneuverability. This fifth wheel type arrangement is well known in this connection, where the tractor element has a chassis with a large coupling shoe extending upwards to mate with a corresponding arrangement on the trailer. A smaller and lighter version is known for towing smaller trailers such as camping trailers, by pickup or other lighter trucks. Here a support frame is mounted to the truck chassis through the truck bed, extending generally upwards to hold a first truck coupling element. A second trailer coupling element extends downward from the forward end region of a trailer to releasably engage the first coupling element. The respective coupling elements may consist of a variety of suitable elements. For example, the truck coupling element may consist of a U-shaped plate mounted generally horizontally to mate with a downwards dependent shoe or ball or kingpin extending from the trailer. Alternatively the relative position of the two elements may be reversed. In the present invention, it is contemplated that any suitable engagement means may be provided at the point of engagement between the trailer and the truck-mounted element.
The invention comprises a bushing having external projections. It also comprises a resilient block held in a frame to form a shock absorbing element, having a cylindrical aperture to receive a pivot pin. Preferably there is a bushing fitting in the aperture to receive the pivot pin. Preferably the bushing has external projections, which together with the bushing are suitably embedded in a resilient block held in a frame to form a shock absorbing element. The shock absorber can be mounted by a bracket on a fifth wheel support frame to receive a pin pivotally mounting the fifth wheel. The structure of the fifth wheel coupling element, the way it is mounted on the support frame, the structure of the support frame, and the way the support frame is attached to the truck chassis through the truck bed, all have multiple possibilities, which while not identical in their effects are generally regarded as equivalents by those skilled in the art, although some are preferred. Alternatively the shock absorber is mounted by a bracket on a cross bar and receives a pin mounted on the support frame. As noted above the bushing may be absent and the pin received in an aperture in the resilient block. Generally the fifth wheel is mounted by a support frame, on the truck chassis through the truck bed, to receive a king pin on the trailer bottom.
Although the invention is described and referred to specifically as it relates to specific devices for bushings, and resilient shock absorber blocks within frames, and devices incorporating such specific devices, it will be understood that the principles of this invention are equally applicable to similar devices and structures for vehicle shock absorbers accordingly, it will be understood that the invention is not limited to such devices and structures for shock absorbers.
A drawback associated with conventional trailer mounting means relates to the high level of shock transmission between trailer and towing vehicle. For instance, when the trailer rides over a bump in the road, shock and displacement impact on the truck through the trailer hitch and vice versa. Such impact and shock transmission results in a rough ride as jolts and vibration are transmitted between trailer and truck, which also tends eventually to damage both vehicles and their contents. Thus, there is a need to provide a means to reduce impact between the trailer and the truck, thereby improving the ride of the towing vehicle and reducing damage to both trailer and truck and their contents.
A typical fifth wheel arrangement varies depending on whether it is integral to a tractor for a semi-trailer, or mounted on a pickup truck. Both variations typically have a truck fifth wheel hook assembly to receive a trailer kingpin. The main difference lies in the support structure which in a tractor for a semi-trailer has trunnions to support the rocker arm pivot pins. The trunnions are usually mounted directly on the tractor chassis. In a pickup truck a support frame is attached to the truck chassis, generally by bolts through the truck bed, with paired spaced apart upstanding arms or legs. The fifth wheel hook assembly is pivotally mounted on the support frame, generally by pivot pins which may be journalled for rotation in two apertures, sleeves or bushings within the support frame. Often the pins rest in U shaped brackets secured by a retaining bolt passed through two apertures in the U bracket. The pivot pins can be directly mounted on the fifth wheel assembly, or the fifth wheel assembly may be fixedly mounted on a cross beam or rocker arm with terminal pivot pins. The pivot pins may be rotatably received directly within support frame arms or legs, or by brackets upon a fixed cross beam, which may form a saddle bracket between support frame arms or legs. In all these arrangements the pivot pins could be mounted on the support frame and received within the fifth wheel coupling arrangement. In practice the pivot pins are usually part of the coupling arrangement. The pivot apertures are often mounted on brackets, which have a vertical array of apertures allowing height adjustable bolting to a similar array of apertures in the support frame arms or legs. The fifth wheel coupling element, or its beam or rocker arm that it is mounted on, rotates about its cross axis allowing pivotal movement in a vertical plane (difference in the angle of fore-aft inclination) between towing vehicle and trailer. The mount or hitch plate or coupler head of the fifth wheel coupling element receives a kingpin, shoe, ball, or other mounting element from the forward end region of the trailer. Generally in all trucks no shock absorber is provided for the fifth wheel hitch. Occasionally a double pivot hitch is used, allowing side to side pivoting of the hitch relative to its cross mounting. This adds a degree of flexibility at extra expense, but has no shock absorbing effect.
U.S. Pat. No. 6,182,966 B1 issued to Koetter et al. Feb. 6, 2001 teaches a fifth wheel hitch mounted by transverse pivot pins having thin bushings of plastic, which are themselves within compressed thin rubber inserts. Pins, plastic bushings and rubber inserts are held within a support recess and a complementary half clip. The pins can have a spherical end embedded within elastic material. The disclosed purpose is to allow limited swinging of the fifth wheel, and twisting of the vehicle frame and for easement of assembly, as the device is not manufactured by precision engineering. It also provides a tight fit for the pivot pins in their bushings. U.S. Pat. No. 6,170,850 B1 issued to Works Jan. 9, 2001, teaches polyurethane pivot bearings about metal pins, mounted atop pedestals for a fifth wheel hitch. The hitch has transverse projecting pivot saddles which engage the pivot bearings. Works provides single or paired side shock absorbers in the hitch head proper. Works"" couple assembly is pivotally mounted on a bearing sleeve around a longitudinal pivot, allowing side to side pivoting. in the absence of shock absorber(s) the hitch would tend to cant to one side or the other. The shock absorber(s) keep the hitch level.
It is also desired to provide an improved means to permit relative rotary movement between a trailer and towing vehicle horizontally about the longitudinal axis of trailer and towing vehicle. When the trailer or towing vehicle experience a limited degree of yaw, it is desirable to permit a degree of freedom of movement about the longitudinal axis of the vehicles.
The principal object of the invention is to provide a shock absorber for a fifth wheel trailer hitch, which will absorb a considerable portion of shock or impact between the trailer and the towing vehicle. A subsidiary object is to provide a shock absorber which will accommodate movement in a vertical plane (pitching). Another subsidiary object is to provide a shock absorber which will accommodate movement in a horizontal plane (yawing)xe2x80x94pivotal movement between trailer and towing vehicle. A further subsidiary object is to provide a shock absorber which will accommodate rotational movement in a cross plane (rolling). In combination these objects provide a degree of shock absorption in three dimensions. A further subsidiary object is to provide a bushing having external projections for a pivot pin. A further subsidiary object is to provide a shock absorber having a frame containing a resilient material having therein a cylindrical aperture to receive a pivot pin. A further subsidiary object is to provide a bushing embedded in said cylindrical aperture. A further subsidiary object is to provide a fifth wheel hitch mounted on support arms or legs attached to a truck chassis through the truck bed, said fifth wheel hitch being mounted by pivot pins inserted into bushings embedded in resilient material contained in a frame. Other objects of the invention will be apparent to those skilled in the art from the following specification, appended claims and accompanying drawings.
In one prototype the invention was tested with bushings embedded in resilient material contained in a metal frame. It was found to work. However while frame and bushing bonded during molding of the resilient material, during cooling there was fractional shrinkage. The bushing came loose from the resilient material, probably, it is thought, because the area of resilient material-frame bonding was much greater than the area of bushing-resilient material bonding. In practice this meant that only the bottom of the bushing engaged the resilient material. This reduced the shock absorber effect, since only compression of resilient material occurred at the bottom of the bushing, there was no comparable extension of resilient material at the top of the bushing. Typically the shock impact is directed downward rather than upward. Although this obviously reduced the shock absorber effect, nevertheless its effect was better than no shock absorber.
The invention in one broad aspect is directed to a bushing for a shock absorber comprising a cylindrical tube with outer radial projections. The shape of the projections is not critical as long as they engage, grasp, grip or embed in resilient material. The projections may be studs or they may be part circular loops circumferential of the cylindrical tube. Typically projections are spaced equally circumferentially. They may be midway axially of the tube when in a single array. In two arrays they will be spaced about a third of the way in from the ends, equidistant axially from each other and opposite ends of the cylindrical tube.
In another broad aspect the invention is directed to a shock absorber comprising a metal peripheral frame spaced apart from and surrounding a planar block of resilient material contacting substantially all the inside surface of the frame. The resilient block has a cylindrical aperture to receive a pivot pin. Preferably, the cylindrical aperture comprises a cylindrical metal bushing to receive a pivot pin. The bushing is embedded in the cylindrical aperture so the planar block of resilient material contacts substantially all the outside surface of the bushing. The planar resilient block extends radially from and embeds the bushing out to the frame, which confines it. The block contacts substantially all the outside surface of the bushing and substantially all the inside surface of the frame. Preferably the bushing has radial bushing projections extending into the material and the frame has inner frame projections extending into the material. The bushing projections may be studs or may comprise at least one array of circumferential loops. Preferably the bushing is central to the resilient block. The frame may be rectangular, when each side comprises at least one projection, typically a lug, or at least one longitudinal array of loops. The shock absorber frame may be integral to a metal mounting bracket. Otherwise a wedge shaped metal corner bracket with an aperture therein to pass a bolt through is attached to each frame corner. A nut is aligned with each aperture to threadably receive the bolt. Typically the corner brackets are welded to the shock absorber frame, covering a portion of the resilient material. Each nut is welded to a corner bracket, and each nut extends into the resilient material. The planar block of resilient material may have an array of apertures/surrounding and parallel to the bushing to increase the compressibility and shock absorbing qualities of the material. The resilient material is preferably memory polyurethane elastomer.
In a third broad aspect the invention is directed to a fifth wheel trailer hitch for a pickup truck. These comprise a support frame mounted on the truck chassis through the truck bed, and a couple assembly. The couple assembly and the support frame both having a pivotal mounting operationally associated therewith. The pivotal mounting has paired shock absorbers each having a metal peripheral frame spaced apart from and surrounding a planar block of resilient material contacting substantially all the inside surface of the frame. The resilient block has a cylindrical aperture to receive a pivot pin. There are paired pivot pins to engage the apertures. Preferably each cylindrical aperture comprises a cylindrical metal bushing to receive a pivot pin. The bushing is embedded in the cylindrical aperture so the planar block of resilient material contacts substantially all the outside surface of the bushing. The resilient block is confined within its surrounding shock absorber metal frame. The shock absorber metal frames may be integral to support brackets mounted on the support frame. The shock absorber metal frames may be attached to support brackets mounted on the support frame. In either case the support brackets are preferably height adjustably mounted on the support frame. Generally the couple assembly is mounted on a cross beam having end pivot pins engaging the bushings of the shock absorbers. Usually each bushing has outer radial bushing projections extending into the material, and the shock absorber frame has inner frame projections extending into the material, which is memory polyurethane elastomer.
The difference between the current shock absorber and a bearing is that the resilient block allows the pivot pin a greater displacement than a bearing, up to forty to fifty percent of pin diameter, or twenty-five to thirty percent of bushing diameter. As those skilled in the art appreciate displacements of this size are rare but occasionally occur under extreme conditions.